In recent years, there has been a trend towards developing less invasive surgical methods, which avoid the trauma and expense of traditional surgical approaches. In minimally invasive surgical techniques, the site of pathology is accessed through portals rather than through a significant incision thus preserving the integrity of intervening tissues. In some cases, these minimally invasive techniques require only local anesthesia, reducing post-operative recovery time and the risk of complications. Many percutaneous procedures have also been developed. The surgical site is accessed through a cannula and visualized either directly, with an endoscope inserted into a cannula or with other visualization means such as fluoroscopic X-ray.
Many developments have also been made in intricate and micro-surgical fields such as surgical ophthalmology and neurosurgery where extreme precision is essential. In these fields, surgical cutting probes are used to separate and remove pathologies from delicate structures. Fine discrimination is required to avoid damaging healthy tissue. Discrimination at this level requires bright lighting and specialized tools.
These new surgical procedures all share common needs: visualization means, a light source and specialized tools. Surgical instruments have been modified in size, shape and character to accommodate the smaller surgical fields. Various visualization and illumination means, such as surgical microscopes and fiber optic microscopes, are commercially available in the field. These advances in surgical tools and procedures have led to a new problem. Surgical instruments typically have a highly reflective surface that causes a glare in the surgical field under the conditions of minimally invasive procedures or micro-surgeries. This glare interferes with proper visualization of the instrument and the surgical field. This is particularly a problem when working with extremely small and delicate structures where even a fraction of a millimeter can be the difference between success and failure.
The glare caused by the reflective surface of ophthalmic microsurgical tools may also aggravate a condition known as light induced retinal damage. Exposure to the intense light of an operating microscope illumination system can cause light induced retinal damage. The onset and severity of light induced retinal damage is thought to be affected by the intensity of light per unit area of retina exposed, the duration of exposure and the wavelength of the light source. Because during eye surgery, it is frequently necessary to directly illuminate the eye with a strong illumination source, eye surgery patients are susceptible to light induced retinal damage. The glare of surgical tools may aggravate this condition by reflecting light and increasing the intensity of the light thereby exposing sensitive eye structures to damaging light. The glare interfering with the surgeon's visualization of the eye structures may also lengthen the duration of the surgery and therefore the duration of exposure to light.
Therefore, a need has remained for surgical instruments that do not interfere with visualization of the microsurgical site. These instruments must address the problem of glare without noticeably increasing the friction characteristics or compromising the durability and strength of the instrument. Furthermore, the instruments must be cost-effective because many of the devices are disposable to eliminate disease transmission risks.
Although there are many known methods for providing surface markings to metal articles, none of these have satisfied this new need for non-glare surgical instruments. Surface treatments can be enveloping or selective. One enveloping method is ebonizing or black oxide surface treatments, which have been used to create black chrome. In such procedures, the article is immersed in acid to etch the surface and then boiled in a caustic black salt bath at high temperatures for about one hour. These methods are harsh and costly for surgical instruments. Laser and electrochemical processes have been used for selective marking of surgical instruments. Lasers have been used to burn the surface of an article to create bands for depth markings and alphanumerics. Electrochemical processes have also been used to create markings on metal articles through the use of stencils or masking. For example, U.S. Pat. No. 4,408,215 to Kitchen discloses selectively marking a surface by selectively firing electrodes through a stencil to mark the surface with alphanumeric characters.
None of these procedures have addressed the problem of surgical glare. Lasers are suited for only selective markings. Darkening a large area by laser dimensionally and structurally changes the article and the large-scale use of laser for darkening an article is impractical and costly. Furthermore, the selective markings currently applied to surgical instruments tend to distort the glare and worsen its effects.
Accordingly, a need has remained for cost-effective means for reducing surgical glare that does not corrupt the integrity of the instrument or increase friction.